1. Field of the Invention
The present invention relates to a storage medium such as a data-recordable disc having a plurality of information recording layers and to a recording/reproducing apparatus and a recording playback method for the storage medium.
2. Description of the Related Art
Optical discs, optical cards, and so on have been known as optical storage media to and/or from which information can be optically recorded and/or reproduced. Information is recorded to or reproduced from such optical storage media by using laser light of a semiconductor laser or the like as a light source, converging the laser light into a tiny light beam through a lens, and illuminating the optical storage media with the light beam.
For the optical storage media, techniques for increasing the recording capacities are under intense development. Conventional approach for increasing the information recording density of optical discs has been focused on increasing the recording density of recording surfaces of the discs. For example, attempts have been made to reduce the track pitch and to increase the recording density in the direction of linear velocity at recording and reading/scanning, in combination with a reproducing operation performed by a reproducing system and a reduction in the wavelength of a light source that emits a recording beam.
However, shortening the wavelength of a light source is limited to an ultraviolet region and the size of pits can only be reduced to a size transferable to a disc during a cutting process. As a result, attempts to improve the recording density will eventually encounter a limit in a two-dimensional disc region.
Accordingly, an approach to increasing the capacity from the three-dimensional perspective has also been made. That is, attention has been directed to a multilayer disc formed by laminating information recording layers to increase the density of recorded information in the disc thickness direction.
A multilayer storage medium having laminated recording layers can multiply the recording capacity according to the number of recording layers and can readily be integrated with another high-density recording technology. As multilayer storage media, for example, DVD-ROM (digital versatile disc read only memory) discs, which are read-only discs, are already put to practical use.
For example U.S. Pat. Nos. 5,682,372, 5,740,136, 5,793,720, and 6,424,614 disclose configurations of read-only optical discs having two recording layers and technologies applicable to recording and reproducing information to and from such optical discs.
In the future, in addition to ROM discs, it is anticipated that recordable multilayer storage media having laminated recordable recording-layers containing phase-change material, magneto-optical material, dye material are put to practical use. For example, in the case of DVD discs, it is also expected that multilayer recording layers are incorporated into write-once discs, such as DVD-R and DVD+R, and rewritable discs, such as DVD-RW, DVD+RW, and DVD-RAM.
Naturally, for a write-once or rewritable multilayer storage medium, user data is recorded in each layer. Thus, a recording apparatus needs to check a maximum position where user data can be recorded (i.e., a maximum address in a region where user data can be recorded) in each layer.
In general, for a write-once recordable disc or rewritable disc, a user-data-recordable region (data zone) is set based on a format, but information of the first address and the maximum address is recorded on the disc. Thus, based on the information, a recording/reproducing apparatus can check a region for the data zone to control a recording operation.
For example, for a dual-layer disc, a data zone exists in both a first layer (layer 0) and a second layer (layer 1) and thus the first address of the data zone is located at a certain address in layer 0 and the maximum address is located at a certain address in layer 1. That is, when only layer 0 is considered, the maximum address of the data zone is not recorded therein.
In essence, however, the maximum address is defined as a disc physical format. Thus, even when the maximum address for each layer is recorded in the disc, this does not directly lead to inconvenience in a recording/reproducing operation. That is, with respect to a disc loaded, it is sufficient for the recording/reproducing apparatus to perform operation by considering the maximum address of a data zone in each layer as an address value defined by the format, without checking a physical address recorded on the disc.
Such a situation, however, is not preferable when future format changes, including an expansion and a change in the recording capacity, are considered.
In order to allow a recording/reproducing apparatus to flexibly deal with format changes of a disc having a plurality of recording layers, the recording/reproducing apparatus needs to be able to easily check the maximum address of a data zone in each layer for each disc.
By way of example, for DVD+R and DVD+RW discs, addresses, which are known as ADIP (ADress In Pre-groove), and physical format information are pre-recorded by wobbling recording tracks.
The physical format information contains the first address and the maximum address of a data zone. For dual-layer discs, however, since a data zone lies across two recording layers, the maximum address of layer 0, which address being logically located at an intermediate position, is not recorded. Thus, the recording/reproducing apparatus performs operation using a maximum address specified by the format, which makes it difficult to deal with a change in the format and so on.